Spark plug



F. FROMMEYER. SPARK PLUG. APPLICATION FILED OCT. -3, 1921.

Patented Nov. 28, 1922.

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FRANK FROMMEYER, OF ST. LOUIS, MISSOURI, ASSIGNOB, BY DIRECT AND MESNE ASSIGNMENTS, TO WOLLO IGNITION PRODUCTS COMPANY, OF ST. LOUIS, MIS- SOURI, A CORPORATION OF MISSOURI.

SPARK PLUG.

Application filed October 3, 3.921. Serial No. 504,837.

To all whom it may concern:

Be it known that I, FRANK FnoMMnYEn, a citizen of the United States, residing at St. Louis, State of Missouri, have invented certain new and useful Improvements in Spark Plugs, of which the following is a from the gap at the ends of the electrodes, .the central electrode thus being divided into two parts, each of which is housed in a suitable porcelain insulator. A further object is to provide a spark plug of this type that is compact, simple in construction, and durable. Further and other advantages will be better apparent from a detailed description of the invention in connection with the accompanying drawings, in which- Figure 1 is a middle longitudinal section through the spark plug, parts being left in elevation; Fig. 2 is a side elevation of the skirt insulator united to the metallic sleeve that secures the same to the plug casing; Fig. 3 is a side elevation of the skirt insulator detached, the same having one part of the central electrode secured in it; Fig. 4c is an enlarged cross-section taken on the line 4l-4 of Fig. 1; Fig. 5 is a side elevation of a modified form of skirt insulator; Fig. 6 is a cross-section taken on the line 66 of Fig. 5.

Referring to the drawings, 1 represents the spark plug casing terminating at one end in a screw-threaded shank for securing the plug in the cylinder head, and at the other end in ahexagonal portion for the application of a wrench, as well understood in the art. A porcelain insulator 2 is disposed in the casing 1, said casing having an annular shoulder 3 formed at about the middle on the inside on which is placed a gasket 3 against which the enlarged portion 2 of the insulator 2 bears. The insulator 2 is traversed by an electrode 4, said electrode being provided with an annular flange 4 about midway between its extremities, said flange bearing against a shoulder Z) formed at the inner end of a chamber a formed in the inner end of the insulator 2. The inner end of the electrode 4, projects beyond the insulator 2 and is provided with screw-threads for the reception of a nut 01 which is turned down tightly against a spring washer w to hold the electrode in the insulator. A shortelectrode 5 projects from the outer end of the casing 1 toward the outer end of the electrode 4: as is well un derstood in the art.

A sleeve 6, having a hexagonal portion 6, is provided at one end with threads for screwing the sleeve into the casing 1, which is threaded to receive the sleeve, said sleeve being provided at the other end with a plain cylindrical portion 6", the wall of which is considerably thinner than the balance of the sleeve. The portion 6" of the sleeve is adapted to receive the reduced portion 7 of a skirt insulator 7, the reduced portion thereof being provided with an annular groove h near its junction with the larger part of the insulator, and being polygonal in shape beyond the groove h. After the reduced portion 7 of the insulator 7 is inserted into the sleeve 6, the cylindrical portion thereof is flattened down on the plane faces (Z of the insulator, and the end of the portion 6 is sWa-ged into the groove h so that the insulator 7 can neither turn in the sleeve 6 nor be separated therefrom.

An electrode 8 is passed through an opening 0 in the insulator 7, the inner end of the electrode being provided with a head on which bears against a shoulder 1 formed in the hollow insulator 7, the electrode 8 terminating at its outer end in a reduced threaded stem 8 for the reception of a nut 17/ and spring washer w for securely holding the electrode 8 in place.

After the sleeve 6 is provided with the insulator 7 and electrode 8, it is screwed into the casing 1 and bears against the enlarged portion 2 of the insulator 2 to hold the same in place, and the inner end of the electrode 4 is telescopically received by a chamber 0 formed in the inner end of the electrode 8, the two electrodes, however, not coming into contact. The electrodes 4 and 8 are thus provided with a gap for increasing the intensity of the spark at the terminals.

In Figures 5 and 6 I show a modified form of insulator 7, the reduced portion 7 of which is provided with a single fiat face d intersecting the groove 7i instead of a plurality of flat faces. The object of the flat face d being to provide a recess into which the metal of the cylinder 6 may be swaged to provide a lock between the sleeve 6 and insulator 7 to prevent relative movement.

Having described my invention, 1 claim:

1. A spark plug comprising a casing, an insulator seated therein, an electrode traversing said insulator, a metallic sleeve screw seated in the casing and operating to hold the insulator therein, a second insulator positioned in said sleeve, an electrode traversing the second insulator and forming a continuation of the first mentioned electrode, said second insulator being provided with a groove interrupted by a plane surface into which the sleeve is swaged for holding the sleeve and insulator against relative movement.

2. A spark plug comprising a casing, an insulator seated therein, an electrode traversing said insulator, a metallic sleeve screw seated in the casing and operating to hold the insulator therein, a second insulator provided with a reduced portion having an annular groove and a fiat face formed on its outer surface, the reduced portion of said insulator being inserted in the sleeve, and the sleeve being swaged over the flat face and into the groove to prevent relative movement of sleeve and insulator.

In testimony whereof I hereunto aifix my signature.

FRANK FROMMEYER. 

